1. Field of the Disclosure
The present disclosure relates to an organic light emitting display device.
2. Description of the Related Art
With the development of an information society, the requirements for display devices have been increased in a variety of manners. In accordance therewith, a variety of flat panel display devices have been researched. The flat panel display devices include liquid crystal display (LCD) devices, plasma display devices (PDPs), electro luminescent display (ELD) devices, vacuum fluorescent display (VFD) devices and so on. Some of the flat display devices are being used in several apparatuses as display devices.
Among the flat panel display devices, the LCD devices are now widely used as portable image display devices in place of cathode ray tubes (CRTs), because of features such as superior image quality, light weight, slimness and low power consumption. Actually, the LCD devices are being developed in a variety of manners. The developed LCD devices are being used in portable devices such as notebooks, television receivers configured to receive and display broadcast signals and desk top computers, as monitors.
FIG. 1 is a planar view showing a thin film transistor substrate of an LCD device according to the related art.
Referring to FIG. 1, a gate line 21 and a data line 31 crossing the gate line 21 are formed on the thin film transistor substrate of the LCD device according to the related art.
A pixel region is defined by the gate and data lines 21 and 31 crossing each other. A thin film transistor T is formed in the pixel region.
The thin film transistor T includes a gate electrode 22, a source electrode 32 and a drain electrode 33. The gate electrode 22 can be formed in a single body united with the gate line 21. The data line 31 can be used as a source electrode 32. The drain electrode 33 can be formed in a shape of “I” running parallel to the data line 21.
A pixel electrode 40 is formed on the pixel region. The pixel electrode 40 can be electrically connected to one end of the drain electrode 33 via a pixel contact hole 50.
The drain electrode 33 partially overlaps with the gate electrode 22. Due to this, a parasitic capacitor Cgd is formed.
FIG. 2 is a waveform diagram illustrating a voltage of a drain electrode of the thin film transistor (i.e., a voltage of the pixel electrode), which is varied by the parasitic capacitor Cgd.
In FIG. 2, a feed through voltage ΔVp corresponds to a difference between a data voltage Vd and a charge voltage Vlc of a liquid crystal cell Clc.
                              Δ          ⁢                                          ⁢                      V            p                          =                                            C              gd                                                      C                gd                            +                              C                lc                            +                              C                st                                              ⁢          Δ          ⁢                                          ⁢                      V            g                                              [                  Equation          ⁢                                          ⁢          1                ]            In the equation 1, “ΔVg” is a difference between a gate high voltage Vgh and a gate low voltage Vgl, and “Cst” is a storage capacitor.
The feed through voltage ΔVp increases as the parasitic capacitor Cgd is enlarged. Due to this, the charge voltage of the liquid crystal cell Clc cannot reach the data voltage Vd.